Devices for manipulating tissue are frequently used in minimally-invasive surgical and diagnostic procedures. Such procedures often involve the use of an endoscope, which allows visualization of the inner structures of a patient without the need for conventional surgery. Manipulation of the tissue is accomplished by passing specialized accessories through a hollow working channel of the endoscope into the inner cavity of the patient, where the accessories can be used to perform functions such as cutting, grasping, snaring, dissecting, cauterizing, and tissue sampling.
One accessory commonly used with endoscopic procedures is forceps. Conventional forceps generally include an effector assembly at the distal end, a control assembly at the proximal end, and one or more control wires extending between the distal and proximal ends. An actuating force is generated at the proximal end by a push-pull mechanism in the control assembly. This force is then transferred to the distal end by pushing or pulling on one or more of the control wires. While the effector assembly is fashioned for the specific function of the device, typically the effector assembly includes a pair of jaws that pivot about a fixed hinge-pin on a support piece. The control wire or wires are linked to the jaws, causing the jaws to open or close as a result of movement of the control wire.
A variety of techniques can be used to link the wires to the jaws. For example, the wire can run through the jaws, and it can be secured to the jaws by a Z-bend that is formed on the distal end thereof. However, this method of attachment creates friction when the jaws are opened and closed, causing the device to operate less fluidly or smoothly than is desirable. The protruding parts commonly resulting from this configuration can also cause damage to the lining of the working channel of the endoscope. Other end effectors are formed using a casting process, and include simple recesses and thru-bores in order to preserve their structural integrity. However, due to the construction of the thru-bores, the drive wire may not be seated precisely within the bore. Rather, the wire usually runs through the bore and is loosely attached by angling or crimping the end alongside the end effector. The resulting jagged or protruding wire could possibly scratch the sensitive lining of an endoscope.
Attempts have been made to overcome the limitations of casted end effectors by refining designs, and in some cases totally abandoning the casting process in favor of machining. Other configurations have been proposed for connecting instrument driving members to instrument end effectors, such as staple-like pins or welded contact points. The drawback to all of the existing connections is a tendency of the parts to wear, and for parts to protrude when the end effectors are in an open position. This hinders smooth, fluid operation of the mechanism and may result in endoscope damage. Moreover, such connections are disadvantageous in that they require labor-intensive assembly.
Accordingly, there remains a need for improved methods and devices for manufacturing an actuator for use in a medical device, and methods and devices for actuating an end effector on a surgical device.